The present invention relates generally to a method for correcting errors in digital audio data, and in particular, to a method for implementing a finite impulse response filter having a sequence of filter coefficients which contains periodic zero-values.
Compact disc players have been in existence for many years. These players read a compact disc and output a sequence of digital audio data. Compact discs typically contain audio information in the form of digitized audio sample data, together with an error correction code, such as a Cross-Interleaved Reed-Solomon code. Most compact disc players use this error correction code in an attempt to correct any errors in the digitized audio samples read from the compact disc. Digitized audio samples with an excessive number of bit errors cannot be corrected using the associated error correction code. Accordingly, the sequence of digital audio data output from compact disc players generally contain a number of erroneous digital audio data samples.
In some cases an additional independent error correction apparatus is appended to the compact disc player in order to correct these excessively erroneous digital audio data samples. These error correction apparatuses generally employ some form of interpolation filter, such as a finite impulse response (FIR) filter, to correct erroneous digital audio data samples. Interpolation filters employ numerous samples surrounding each erroneous sample in an attempt to determine the correct value for the erroneous sample and replace the erroneous sample with a reconstructed value.
One problem with some prior art methods employing interpolation filters, such as FIR filters, is that some of the digital audio data samples surrounding the "known" erroneous sample may also be erroneous. Application of a interpolation filter which utilize these additional erroneous samples to reconstruct the current erroneous sample results in increased interpolation error in the output. In effect, the additional erroneous samples are "propagated into" the "corrected" value which is output from the interpolation filter.
Accordingly, it is an object of the present invention to provide a method for correcting errors in a sequence of digital audio data which minimizes the propagated error by employing a FIR filter which contains periodic zero-valued filter coefficients.
It is a further object of the present invention to provide a method for correcting errors in a sequence of digital audio data by employing a FIR filter containing periodic zero-valued filter coefficients, wherein the locations of the zero-valued coefficients correspond to the likely locations of the additional erroneous digital audio data samples.
These and other objects of the present invention will become apparent in light of the present specification and drawings.